filter-pub-test filters "pub run test" output to make it Emacs-friendly

filter-pub-test.go

// -*- compile-command: "go build filter-pub-test.go"; -*-

// filter-pub-test filters out the ANSI color codes from "pub run test" output.
// It also changes the output so that Emacs understands what file, line, and column
// numbers had the error so it can jump to the next error directly with "C-x `".
package main

import (
	"bufio"
	"bytes"
	"log"
	"os"
	"regexp"
	"strings"
)

var (
	toRemove = []string{
		"\x1b[0m",
		"\x1b[1;30m",
		"\x1b[1m",
		"\x1b[31m",
		"\x1b[32m",
	}

	crRE          = regexp.MustCompile(`\s+\r`)
	timeRE        = regexp.MustCompile(`^\d\d:\d\d `)
	fileLineColRE = regexp.MustCompile(`^\s+\S+\.dart \d+:\d+ `)
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(ScanLines)

	var lines int
	for scanner.Scan() {
		lines++
		buf := scanner.Bytes()
		s := crRE.ReplaceAllString(string(buf), "\r")
		for _, r := range toRemove {
			s = strings.Replace(s, r, "", -1)
		}
		s = timeRE.ReplaceAllStringFunc(s, func(v string) string { return strings.Replace(v, ":", ";", -1) })
		s = fileLineColRE.ReplaceAllStringFunc(s, func(v string) string {
			v = strings.TrimLeft(v, " ")
			return strings.Replace(v, ".dart ", ".dart:", -1)
		})
		os.Stdout.WriteString(s)
	}

	if err := scanner.Err(); err != nil {
		log.Fatalf("scanner: %v", err)
	}
}

func ScanLines(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	if i := bytes.IndexByte(data, '\r'); i >= 0 {
		// We have a full line terminated by a carriage return.
		return i + 1, data[0 : i+1], nil
	}
	if i := bytes.IndexByte(data, '\n'); i >= 0 {
		// We have a full newline-terminated line.
		return i + 1, data[0 : i+1], nil
	}
	// If we're at EOF, we have a final, non-terminated line. Return it.
	if atEOF {
		return len(data), data, nil
	}
	// Request more data.
	return 0, nil, nil
}